Arc welding monitoring device

ABSTRACT

The invention provides an arc welding monitoring device by which it is possible to easily find how detected data such as a welding current and welding voltage correspond to trajectories of a robot, in other words, welding line information of a welding work. The arc welding monitoring device comprises means  4  and  5  for detecting at least either the welding current or welding voltage, a means  14  for storing the detected data, a means  14  for storing trajectories of a robot, and a means for displaying, on a screen display, at least either the welding current or welding voltage detected by said detecting means, and the trajectories of the robot stored by the storing means, wherein a range is determined on the trajectories displayed on the screen display, and arc welding monitoring display is enabled in compliance with the range.

FIELD OF THE INVENTION

The present invention relates to an arc welding monitoring device whichmonitors arc welding and controls welding quality.

DESCRIPTION OF THE RELATED ART

Conventionally, as a device for monitoring arc welding, there has been awelding monitoring device which detects a welding current and a weldingvoltage during welding, distinguishes whether or not the detected dataare within the predetermined range, and issues an alarm when either ofthe detected data is outside the range. For example, this method isdisclosed by Japanese Patent Publication No. 7-2275. In Japanese PatentPublication No. 7-2275, in a device for monitoring arc welding by an arcwelder, an arc welding monitoring device is disclosed, which comprises ameans for detecting a welding current or an arc voltage, and A/Dconverter for converting analog output signals of the detecting means todigital signals in terms of a sampling frequency, a means for setting anoperator period and fluctuation pitch to obtain a fluctuation mean, ameans for setting a monitoring value to monitor the fluctuation meanvalue of the welding current or arc voltage, a means for judging weldingconditions or welding results by comparing the fluctuation means valueof the welding current or arc voltage with monitoring values, and ameans for displaying and outputting the judgement results of the judgingmeans. FIG. 3 shows one example of display screens of the detected dataat this time, wherein the abscissa indicates a welding current, awelding voltage, and the ordinate indicates a period of time of welding.That is, this drawing is a graph showing changes in a welding currentand a welding voltage with respect to welding time.

However, where, in welding made by an arc welding robot, weldingconditions are monitored by a prior art welding monitoring device, it ispossible to recognize whether or not any welding defect occurred, byacquiring changes in the welding current and welding voltage withrespect to the elapse time of welding as shown in FIG. 3. However, it isnot possible to understand which program of the robot has been used, inother words, which kind of a welding work has been welded. Inparticular, in a case where a complicated work is welded, by using anarc welding robot, it was difficult to know at which part of the weldingwork a defect occurred even though a welding defect is detected by thewelding monitoring device. To the contrary, in a case where a weldingdefect is found by observing the welding work, there is a case where itis desired to analyze how the then welding current waveform or weldingvoltage form are brought about. But, in such a prior art weldingmonitoring device, it is not clear to which part of the detected datathe welding current and welding voltage corresponding to the rangeselected by a welding work belong.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an arcwelding monitoring device by which it is possible to easily find thetrajectories of a robot, in other words, how detected data such aswelding current and a welding voltage, etc., correspond to welding lineinformation of a welding work.

In order to achieve the above object, a first arc welding monitoringdevice, according to the present invention, is featured in beingprovided with, in an arc welding robot controlling device, a means fordetecting at least either of a welding current or a welding voltage, ameans for storing the detected data and trajectories of a robot, a meansfor displaying at least either of the welding current or welding voltagedetected above on a display, and the trajectories of the robot stored bythe abovementioned means, and a means for setting a range of displayingthe detected data on the display.

A second arc welding monitoring device, according to the presentinvention, is featured in that parts of trajectories of the robotdisplayed on the above display are set by designating the parts thereofin the means for setting a range of displaying the detected data on theabove display.

A third arc welding monitoring device, according to the invention, isfeatured in that, in the means for setting a range of displaying theabovementioned detected data on the above display, the setting iscarried out by designating the range of data of the welding current orwelding voltage, and parts of trajectories of a robot, which aredesignated above, are displayed with a different color from that of theother remaining parts thereof.

A fourth arc welding monitoring device, according to the invention, isfeatured in having a means for setting conditions of judgingabnormalities in welding, and a comparator for comparing the conditionsset by the setting means for judging abnormalities with the detecteddata, wherein, in a case where any abnormality or defect occurs whenmonitoring the detected data and judging any abnormality or defect, therange of data which was judged as abnormal welding is displayed with adifferent color from that of the other range.

A fifth arc welding monitoring device is featured in that the detectedand stored data are date obtained by various types of sensors other thanthe welding current and welding voltage.

According to an arc welding monitoring device disclosed by theinvention, the following effects and advantages can be obtained; wherein

(1) Welding current and welding voltage are correlated with and storedalong with robot operation programs, wherein since not only a weldingcurrent and a welding voltage but also trajectories of the robot usedfor welding are displayed on a display screen it is possible to easilyfind to which welding work the welding current and welding voltage datacorrespond, or how welding lines of the welding work are taught.

(2) Since it is possible to check which part of data of the trajectoriesof a robot the data such as a welding current and welding voltage, whichare displayed on a display screen, display, any unstable portion of thewelding condition can be specified, and it is possible to find portionsat which the welding conditions are to be changed or the welding postureof a robot is to be changed, thereby contributing to improvement in thewelding quality.

(3) Since it is possible to specify a portion of abnormal or defectivewelding, it is sufficient to check the portions which are judgedabnormal or defective, when conducting a visual defect detection onwelding work.

(4) Since data such as a welding current and welding voltage atappointed portions of welding work can be displayed, it is possible tofind patterns of the welding current and/or welding voltage at theportions where any abnormal or defective welding is visually found.Therefore, it is effective to analyze the arc welding phenomenon.

(5) It is also possible to monitor information such as, for example,wire feeding speed, gas flow rate, etc., in addition to the weldingcurrent and welding voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general configurational view of a preferred embodiment ofthe invention,

FIG. 2 is a view showing the outline of an abnormal welding judgementprocessing portion of the preferred embodiment of the invention,

FIG. 3 is a description of a screen display of a welding current and awelding voltage, which are displayed on a monitor screen, in a prior artarc welding monitoring device,

FIG. 4 is an example of a screen display of the welding current, weldingvoltage and trajectories, which are displayed on a monitor screen by anarc welding monitoring device of the present invention, and

FIG. 5 is another example of a screen display of the welding current,welding voltage and trajectories, which are displayed on a monitorscreen by an arc welding monitoring device of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a description is given of an arc welding monitoring deviceas a preferred embodiment of the invention. FIG. 1 is a generalconfigurational view of a system for carrying out the invention, wherein1 is a robot controlling device, 2 is a welder, 3 is a torch attached toa robot (not illustrated), and 12 is a monitoring device.

Hereinafter, a description is given of an operation flow of weldingexecution and detection of a welding current and a welding voltage. Anarc is generated by applying voltage, which is provided by the welder 2,between parent metal 10 and the torch 3, whereby a welding bead isformed by moving the torch 3. At this time, a current detector 4 detectsthe welding current, and a voltage detector 5 detects the weldingvoltage. The detected welding current and welding voltage are inputtedinto low-pass filters 6 and 7, wherein high frequency components (noise)are removed. And the data are converted to digital values by A/Dconverts 8 and 9 and are picked up into the robot controlling device 1.The picked up welding current and welding voltage are variously operatedand processed by a central processing unit (hereinafter called “CPU”)11, whereby the arc state is monitored in compliance with various typesof algorithms, and the picked up welding current and welding voltage areadequately stored in a storing portion 14. The trajectory information ofthe robot is acquired by a locus position detector 13 in the robotcontrolling device 1, and the information is stored in the storingportion 14.

In the first preferred embodiment, a motion simulation of a robot iscarried out on the display of the monitoring device 12 based on therobot trajectory information stored in the storing portion 14, and atrajectory of the robot is displayed thereon. Simultaneously, thewelding current and welding voltage stored in the storing portion 14 aredisplayed on the display of the monitoring device 12, whereby it ispossible to not only observe changes in the welding current and weldingvoltage but also check the movement programs of the robot, whereby it ispossible to find a pattern of a welding line of a welding work.

In the second preferred embodiment of an arc welding monitoring device,a robot movement simulation is carried out on the display of themonitoring device 12 based on the robot trajectory information stored inthe storing portion 14, whereby the robot trajectory is displayed. As amethod for setting a range of screen displays of the welding current andwelding voltage stored in the storing portion 14 on the display when thetrajectory of a robot is displayed, for example, a mouse may be used asa peripheral input device. By setting a range of trajectories for whichchange in the detected data are required to be checked, using a mouse,the contents of the welding current and welding voltage data in a rangecan be displayed on the display of the monitoring device 12. FIG. 4shows one example of the screen displays at this time. In the drawing,the upper stage indicates the trajectories of a robot while the lowerstage indicates changes in the welding current and welding voltage. Inthe same drawing , the robot moves in the order of step 1, step 2, step3, step 4, wherein step 1 is the initiating point of welding and step 4is the terminating point of welding while steps 2 and 3 are points ofteaching. Herein, the range depicted by the thick line between step 1and step 2 indicates the selected range for indicating waveformsselected by an inputting device such as a mouse, etc., whereby anoperator can easily find the contents of the welding current and weldingvoltage data at the designated points of welding work by onlydesignating a range of trajectories corresponding to the welding work.

In the third preferred embodiment of an arc welding monitoring device,as in the second embodiment, a motion simulation is carried out on thedisplay of the monitoring device 12 based on the robot trajectoryinformation stored in the storing portion 14. And, the welding currentand welding voltage stored in the storing portion 14 are concurrentlydisplayed on the display. There is a case where it is necessary to checkto which part of trajectories a certain range of data of the weldingcurrent and welding voltage displayed on the display corresponds. Insuch a case, for example, the cursor is displayed on the welding currentand welding voltage graph, whereby the data range is designated. Thetrajectory portion corresponding to the range is displayed with, forexample, a color different from that outside the range, whereby it isthen possible to distinguish to which portion of the trajectories theselected range of the welding current and welding voltage data belong.FIG. 5 shows one example of display screens at this time. In the samedrawing, the upper stage indicates trajectories of the robot while thelower stage indicates changes in the welding current and weldingvoltage. In the same drawing, the robot moves in the order of step 1,step 2, step 3, and step 4, wherein step 1 is the initiating point ofwelding and step 4 is the terminating point of welding while steps 2 and3 are points of teaching. Herein, the range depicted by the thick linebetween step 1 and step 2 expresses an area in which the welding currentand welding voltage in the range selected by the cursor at the lowerstage in FIG. 5 are obtained. Thereby, where an extraordinary point isfound in changes in the patterns of the welding current, welding voltagedata, etc., it is possible to easily distinguish to which part of thetrajectories or the welding work the data correspond.

In the fourth preferred embodiment, welding state monitoring can becarried out by further adding a portion for processing judgement of awelding abnormality to the second and third embodiments. FIG. 2 is ablock diagram of one preferred embodiment of the portion for processingjudgement of a welding abnormality. Judgement of a welding abnormalityis carried out by a welding abnormality judging device 22 in the robotcontrolling device 1. The welding abnormality judging device 22 consistsof a welding abnormality judging condition setting device 24, comparator23, and an output device 25 of welding abnormality judgement results.Data acquired by various types of sensors are picked up into a sensordata input portion 21, wherein the picked up data are compared by thecomparator 23 with reference values predetermined by the weldingabnormality judging condition setting device 24. Unless the detecteddata are within the abovementioned reference values, information onoccurrence of a welding abnormality is stored in the storing portion 14by the output device 25 of welding abnormality judgement results.Further, simultaneously, an abnormality detecting signal is outputted toa peripheral device by a peripheral alarm device 26, in order to notifythat an abnormality has occurred. In addition, as an algorithm forjudging a welding abnormality, the number of times of shortcircuiting,mean welding current value, mean welding voltage value, etc., may beutilized. With respect to displaying of the measured data by themonitoring device 12, a motion simulation is carried out on the displayon the basis of the robot trajectory information stored in the storingportion 14 as in the second and third preferred embodiments.

In the fifth preferred embodiments, it is possible to concurrentlydisplay, on the display, information obtained by various types ofsensors, such as, for example, a wire feeding speed, gas flow rate,etc., including various types of measured data other than the weldingcurrent and welding voltage stored in the storing portion 14. Theportion which is judged abnormal, of various types of measured datadisplayed on the display is indicated with a color different from thatin a normal case. Further, with respect to the trajectories, a portionwhich is judged abnormal is indicated with a color different from thatin a normal case, whereby it is possible to easily distinguish to whichrange of data the portions which are judged abnormal in changes in thepatterns of various types of measured data belong, or at which part ofthe trajectories, that is, the welding work, it is abnormal.

[Industrial Applicability]

The present invention relates to an arc welding monitoring device whichtakes roles of monitoring welding states and controlling the weldingquality, in an arc welding robot system.

What is claimed is:
 1. An arc welding monitoring device of an arcwelding robot controlling apparatus, comprising: detecting means fordetecting electric signals consisting of either a welding current or awelding voltage; storing means for storing said detected weldingelectric signals and trajectories of a robot; display means fordisplaying, on a screen display, either the welding current or weldingvoltage detected by said detecting means and trajectories of a robot,which are stored by said storing means; and a means for setting a rangeof data of said welding current or said welding voltage to be displayed.2. An arc welding monitoring device as set forth in claim 1, whereinsetting is carried out by designating the portion of the trajectories ofthe robot, which is displayed on said screen display.
 3. An arc weldingmonitoring device as set forth in claim 1 or 2, wherein setting iscarried out by designating said range of data of said welding current orsaid welding voltage, and the portion of the trajectory of the robot atthe range-set position is indicated with a color different from that ofthe other remaining portion.
 4. An arc welding monitoring device as setforth in claim 1 or 2, further comprising: setting means for settingjudgement conditions of a welding abnormality; and a comparator forcomparing the conditions established by said setting means with saiddetected data, wherein, whenever any abnormality is found to have beengenerated by monitoring said detected data and judging a weldingabnormality, the range of data in which a welding abnormality occurredis displayed on the trajectory with a color different from that of theother remaining range.
 5. An arc welding monitoring device as set forthin claim 1 or 2, wherein said storing means stores data acquired byvarious types of sensors in addition to the welding current and thewelding voltage.